The "beads-on-string" structure seen under an electron microscope refers to?
Chromatin fibers viewed under an electron microscope appear as beads on a string, where the beads are nucleosomes and the string is the linker DNA.
Question 152 of 668
📘 CLASS XII
Which scientist(s) conducted the "Transforming Principle" experiment?
Frederick Griffith conducted the experiments with Streptococcus pneumoniae and mice in 1928, discovering the Transforming Principle.
Question 153 of 668
📘 CLASS XII
In Griffith's experiment, mice died when injected with?
Mice survived injection with heat-killed S strain alone and live R strain alone. However, the mixture of both caused death because the R strain was transformed into virulent S strain by DNA from the heat-killed S strain.
Question 154 of 668
📘 CLASS XII
The S-strain of Streptococcus pneumoniae is virulent because?
The S-strain (Smooth) possesses a smooth polysaccharide mucous coat that protects it from the host's immune system, allowing it to cause pneumonia.
Question 155 of 668
📘 CLASS XII
Avery, MacLeod, and McCarty proved that the transforming principle was?
They purified biochemicals from the heat-killed S cells and found that only DNA—and its digestion by DNase—prevented transformation, proving DNA was the transforming agent.
Question 156 of 668
📘 CLASS XII
Why was the Hershey-Chase experiment considered the "unequivocal proof" of DNA as genetic material?
By using radioactive Sulfur (for protein) and Phosphorus (for DNA), they showed conclusively that only DNA enters the bacterial cell to direct viral reproduction, ruling out protein entirely.
Question 157 of 668
📘 CLASS XII
In the Hershey-Chase experiment, radioactive Sulfur-35 labeled the?
Sulfur is present in amino acids (cysteine, methionine) found in proteins but not in DNA. Thus, S-35 labeled the viral protein capsid.
Question 158 of 668
📘 CLASS XII
Radioactive Phosphorus-32 labels DNA because DNA contains?
DNA contains a phosphate backbone. Phosphorus is not found in proteins (usually). Thus, P-32 specifically labels DNA.
Question 159 of 668
📘 CLASS XII
Which step involves the agitation of viral coats from bacterial cells in the Hershey-Chase experiment?
Blending is the mechanical agitation step used to shear off the empty viral protein coats (capsids) from the surface of the bacterial cells after infection.
Question 160 of 668
📘 CLASS XII
The genetic material in Tobacco Mosaic Virus (TMV) is?
TMV is a classic example of a virus that uses RNA as its genetic material, alongside QB bacteriophage.
